Madrid, Spain (CNN) -- Al Qaeda in the Islamic Maghreb (AQIM) said Tuesday it was holding three Spanish aid workers kidnapped late last month in Mauritania, and Spain's Foreign Minister said the government considered the claim "credible."

In an audio recording released Tuesday on al Jazeera television, AQIM "specifically mentioned the names" of the three aid workers, the Foreign Ministry said in a statement released in Madrid.

Later at a news conference in Brussels, Foreign Minister Miguel Angel Moratinos said, "Based on the information we have, we consider credible that claim of responsibility."

The al Qaeda message Tuesday set no immediate conditions for the release of the three, saying that would come in a future message to the Spanish government, the foreign ministry statement said.

"We have to wait for that contact, which has not happened yet, and we keep working to free our nationals," Moratinos said.

The two men and a woman, from the Barcelona Solidarity Action humanitarian organization, were kidnapped November 29 in Mauritania from a 13-vehicle aid convoy. The Spanish government said the next day it suspected al Qaeda.

"Minutes before 7 a.m. today (Tuesday), al Qaeda in the Islamic Maghreb, on al Jazeera television, claimed responsibility for the kidnapping of the Spanish aid workers in Mauritania and for a French citizen in Mali," the foreign ministry statement said.

Relatives of the three Spanish hostages were informed of the claim soon after by the Spanish government, the foreign ministry statement said.

Various radical Islamist Web sites later carried the al Qaeda message, which stated that two mujahedeen cells abducted the Westerners -- the three Spaniards about 170 kilometers (105 miles) north of Mauritania's capital Nouakchott, near Nouadhibou, and the Frenchman in neighboring Mali, to the east.

The Spanish government has enlisted the aid of the governments in Mauritania and Mali to help free the hostages, and Spain sent aircraft for that effort.

The three Spanish aid workers were in a vehicle toward the end of the convoy, which became separated from the rest. Their colleagues soon noticed their absence and went back to find the vehicle, which was empty, with the doors open, and with tracks from another vehicle leading away into the desert, Spanish officials said.

The aid agency and the three people kidnapped are well known in Barcelona.